CVE-2026-26824: libxls through version 1.6.3 contains a use of uninitialized memory vulnerability in the OLE container parser

Q: How do I fix CVE-2026-26824?

libxls: upgrade to newer than 1.6.3. Exact commands for each OS are on this page.

Q: Is CVE-2026-26824 being exploited?

CVE-2026-26824 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-26824 affect?

CVE-2026-26824 affects libxls. Severity is medium (CVSS 6.5). libxls through version 1.6.3 contains a use of uninitialized memory vulnerability in the OLE container parser. Memory allocated for the Master Sector Allocation Table (MSAT) in read_MSAT() is not fully initialized before being consumed by o

Q: How urgent is CVE-2026-26824?

Priority 38/100. Public exploit reference; Remotely exploitable, no login, no user action

This week

MEDIUM 6.5REMOTEUPGRADE

CVE-2026-26824 is a medium-severity flaw (CVSS 6.5) affecting libxls. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

libxls through version 1.6.3 contains a use of uninitialized memory vulnerability in the OLE container parser. Memory allocated for the Master Sector Allocation Table (MSAT) in read_MSAT() is not fully initialized before being consumed by ole2_validate_sector_chain(), which may result in application crashes or potential information disclosure when processing a crafted XLS file

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 81%)
CISA exploited list	No
Weakness	CWE-457
Published	2026-06-03
Last modified	2026-09-23

Publisher (CNA): MITRE · Vendor: libxls project

Last updated 2026-09-23 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-03 20:16 UTCPublished CVE record published
2026-09-23 16:16 UTCUpdated Record last modified

libxls project libxls UPGRADE

Affected: <= 1.6.3

Fixed in: newer than 1.6.3

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy libxls || rpm -q libxls || libxls --version

2. UPGRADE to newer than 1.6.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade libxls

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libxls

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-26824?

libxls: upgrade to newer than 1.6.3. Exact commands for each OS are on this page.

Is CVE-2026-26824 being exploited?

CVE-2026-26824 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-26824 affect?

CVE-2026-26824 affects libxls. Severity is medium (CVSS 6.5). libxls through version 1.6.3 contains a use of uninitialized memory vulnerability in the OLE container parser. Memory allocated for the Master Sector Allocation Table (MSAT) in read_MSAT() is not fully initialized before being consumed by o

How urgent is CVE-2026-26824?

Priority 38/100. Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-26825 MEDIUM 5.3 DOWNGRADE A use-of-uninitialized memory vulnerability exists in libxls 1.6.3 when parsing malformed XLS files

References

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